Nitric oxide synthases (NOS) catalyze the 5-electron oxidation of L-Arg to nitric oxide (NO) and L-citruline. NO is a key molecular signal and neurotransmitter. Three different isozymes are present in the body- iNOS, eNOS, and bNOS. Many pathologies have been linked to either excessive or insufficient NO production. Thus, isozyme specific inhibitors are desirable from a medicinal point of view. The goal of this project is to determine structures of inhibitor bound complexes and to apply the structural information to the design of isozyme specific inhibitors.